Measurement of paper stack topography

Abstract

This is a probe that can be used to measure any curl on a stack of sheets in a sheet stacking tray. In printing systems including electrophotographic systems, sheets tend to curl on edge portions. This curl can adversely affect the final copy and copies fed to finishing stations. This probe lightly contacts the upper stack surface and detects sheet curl especially on the edge portions of the stack. The probe measures deviations of the surface as compared to a starting point defined on the terminal edge of the stack. The information provided by the probe is then fed to a user or controlled for transmission to a correcting apparatus.

1. A method for measuring the curl of a sheet of paper on a top of a substantially stationary stack of paper sheets comprising:
 positioning a horizontally movable probe over said stack; 
 positioning said probe on a movable actuator transport; 
 moving said probe across a top surface of the stack along an axis substantially parallel to one edge of the stack; 
 exerting a controlled low contact force where said force is insufficient to deform said stack surface; 
 providing a sensor to measure said probe's angular displacement and direction of motion across said stack; 
 providing a controller in informational contact with said sensor; 
 recording via said sensor the height of the probe relative to a reference height; and transmitting the recorded height measurements to said controller. 
 
   
   
     2. The method of  claim 1  wherein said probe is moved over curls and rises on said stack surface and measures them when compared to a probe starting location. 
   
   
     3. The method of  claim 1  wherein said probe is provided as a suspended probe that has a probe force when in contact with said stack surface which is insufficient to deform said stack surface whereby said probe thereby conveys a true topography of said stack surface to a controller.